FIELD OF THE INVENTION
This invention relates Lo a method of making cellulose ester photographic film base and more particularly to a method of preparing photographic film base having fewer imperfections than the methods currently employed which method is conducted in a much shorter period of time.
It is known in the art to prepare cellulose ester photographic film base materials by casting a cellulose ester solution or dope in the form of a film on a highly polished surface of a rotating wheel or band, causing the film to set by evaporation of a portion of the volatile solvent present in the casting solution, stripping the film from the casting wheel or band while it still contains a high percentage of solvent but has sufficient strength to maintain its form and then drying the film by passing it through various chambers while directing hot air over the surface thereof as the film is continuously transported by numerous rollers until the final and desired state of dryness is reached. Then the film base is wound upon itself in a roll for further processing into photographic element.
A problem chat accompanies this process is that as the utility for the film base is in the production of photographic film of all types, any imperfections that are present in the film will be carried over into the final product. Thus, rigid inspection methods must be employed and any imperfections Chat are present in the film base must be removed before the base can be employed as the substrate upon which photographic elements are built. As each of the rollers over which the film base passes during the drying cycle can be a source of imperfections in the film base, it is desirable to reduce the number of such rollers to a minimum and at the same time shorten the preparation time for the cellulose ester film base.